Surge protectors

[Brian63]

We bought a new TV recently and want to protect it with strong surge protection. We have the option of buying one brand new. Let's say that we want it to be able to handle 900 joules. Instead of getting a single surge protector that handles that amount, would it work just as well to use several smaller surge protectors that add up to that amount? They could be plugged into each other in a chain, for instance. Ignore for the moment any concerns about clutter of multiple surge protectors or cosmetics or such. Only in terms of efficacy, would it work as fine to use 1 surge protector of 200 joules, another of 250 joules, and another of 450 joules?

 

[barbos]

Assuming they are not faulty, total amount is what matters.
In reality, surge protectors are effectively crowbars which cause overcurrent which blows fuse/switch and disconnects you from the lane. So in theory you need just certain amount above which it become unnecessary. But if thunderbolt hits you directly then all bets are off.

 

[barbos]

Some manufacturers commonly design higher joule-rated surge protectors by connecting multiple MOVs in parallel and this can produce a misleading rating. Since individual MOVs have slightly different voltage thresholds and non-linear responses when exposed to the same voltage curve, any given MOV might be more sensitive than others. This can cause one MOV in a group to conduct more (a phenomenon called current hogging), leading to possible overuse and eventual premature failure of that component. However the other MOVs in the group do help a little as they start to conduct as the voltage continues to rise as it does since a MOV does not have a sharp threshold. It may start to short at 270 volts but not reach full short until 450 or more volts. A second MOV might start at 290 volts and another at 320 volts so they all can help clamp the voltage, and at full current there is a series ballast effect that improves current sharing, but stating the actual joule rating as the sum of all the individual MOVs does not accurately reflect the total clamping ability. The first MOV may bear more of the burden and fail earlier. One MOV manufacturer recommends using fewer but bigger MOVs (e.g.60 mm vs 40 mm diameter) if they can fit in the device and to match them and derate them. In some cases it may take four 40 mm MOVs to be equivalent to one 60 mm MOV.[8]

Surge protector - Wikipedia

en.wikipedia.org

Explains why one bigger one is better than few smaller one.

 

[steve_bank]

It depends on the type. If the surge protectors use the TVS (transient voltage suppressors) devices yes.

Put two in parallel and under a transient one will start conducting first. As the voltage rises on the first at some point the other will conduct sharing current. Essentially back to back Zener diodes.

Cheaper MOVs not so much. They degrade with transients.

Surge protector - Wikipedia

en.wikipedia.org

If you really want to protect an expensive TV you could build your own. Parts are cheap. Plams on the net.

If you buy them make sure they are UL listed or certified to an ISO standard, should be on the label. I expect there is a lot of junk supresors out there.

Electronics these days are usually tested against an international surge standard. TVS is part of the power supply.

 

[barbos]

Cheaper MOVs not so much

TVS I understand are really zenner diodes, they are low voltage and usually used for protecting data lines in network connections and such. They are small.
MOV are different devices for protecting power lines, they are high voltage and high energy spikes.

 

[ZiprHead]

Something my sister didn't know and it cost her, when the light on the supressor starts twinkling that means the supressor is worn out and needs to be replaced.

 

[steve_bank]

Transients come from lightning and grid switching events.

If you live near an industrial area especially in the morning and evening there will be transients as equipment is turned on and off. In the 70s I knew somebody whose stereo and tun table would fail from local transients, so he added MOVs at the AC inputs.

TVs these days should be able to deal with routine events. In the early days of PCs a line transient could feed through the power supply and crash the computer. That should not happen anymore.

A nearby direct lightning strike on a power line is locally catastrophic and takes special protection like lightning arrestors on the service entrance.

 

[Cheerful Charlie]

There are consumer power strips and then there are industrial power strips. You will pay more for the latter. Decisions, decisions.